Industry Segment Information (Schedule of Sales and Operating Income by Operating Segment, Excluding Discontinued Operations) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011
Segment Reporting Information [Line Items]
Revenue	$ 521,790,000	$ 479,065,000	$ 1,032,680,000	$ 926,243,000
Operating income (loss) from continuing operations	49,787,000	39,419,000	86,169,000	80,850,000
Interest and other expense, net	11,358,000	4,271,000	24,188,000	10,027,000
Income from continuing operations before income taxes	38,429,000	35,148,000	61,981,000	70,823,000
Document Period End Date			Jul. 01, 2012
Sales Revenue, Goods, Net	364,243,000	326,419,000	721,436,000	632,545,000
Sales Revenue, Services, Net	157,547,000	152,646,000	311,244,000	293,698,000
Human Health [Member]
Segment Reporting Information [Line Items]
Revenue	258,422,000	218,817,000	512,383,000	420,138,000
Operating income (loss) from continuing operations	31,538,000	28,446,000	53,483,000	49,983,000
Sales Revenue, Goods, Net	219,721,000	185,480,000	435,550,000	354,226,000
Sales Revenue, Services, Net	38,701,000	33,337,000	76,833,000	65,912,000
Environmental Health [Member]
Segment Reporting Information [Line Items]
Revenue	263,368,000	260,248,000	520,297,000	506,105,000
Operating income (loss) from continuing operations	28,159,000	21,748,000	54,554,000	51,990,000
Sales Revenue, Goods, Net	144,522,000	140,939,000	285,886,000	278,319,000
Sales Revenue, Services, Net	118,846,000	119,309,000	234,411,000	227,786,000
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income (loss) from continuing operations	(9,910,000)	(10,775,000)	(21,868,000)	(21,123,000)
Method of Recognition of Defined Benefit Pension and Other Postretirement Benefits [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments			$ 1,200,000	$ (200,000)